Hi, all I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob. Is there a good way to tell if the mirror is worth the effort to make a dob built around it? I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.) The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so. If some one has a mirror cell to fit this size of mirror I would love to hear from you. I really do not know what I should be looking for to check the mirror. Any Suggestions would be appreciated. Mark
Mark, a quick look through a Ronchi grid will tell you everything. Likewise, before you part-out the Coulter, perform a star test. That will also tell you about the correction on the parabola. I have owned many Coulter mirrors over the years, and never had a bad one. On 1/24/11, Mark Shelton <woodturninginc@yahoo.com> wrote:
Hi, all
I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob.
Is there a good way to tell if the mirror is worth the effort to make a dob built around it?
I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.)
The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so.
If some one has a mirror cell to fit this size of mirror I would love to hear from you.
I really do not know what I should be looking for to check the mirror.
Any Suggestions would be appreciated.
Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
Mark, Have you considered emailing Steve Dodds over at Nova Optical here in Herriman? I know when my daughter and I get done figuring our 8" and 12" mirrors I'll have him coat them. I believe he can test the mirror for you. How old is the mirror and how do the coatings look? Jay On Mon, Jan 24, 2011 at 2:29 PM, Chuck Hards <chuck.hards@gmail.com> wrote:
Mark, a quick look through a Ronchi grid will tell you everything. Likewise, before you part-out the Coulter, perform a star test. That will also tell you about the correction on the parabola.
I have owned many Coulter mirrors over the years, and never had a bad one.
On 1/24/11, Mark Shelton <woodturninginc@yahoo.com> wrote:
Hi, all
I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob.
Is there a good way to tell if the mirror is worth the effort to make a dob built around it?
I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.)
The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so.
If some one has a mirror cell to fit this size of mirror I would love to hear from you.
I really do not know what I should be looking for to check the mirror.
Any Suggestions would be appreciated.
Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
-- Jay Eads
Hi, I will go out and clean the mirror tonight sometime and take a close look. I will let you know what it looks like. Thanks for the information Mark ________________________________ From: Jay Eads <jayleads@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Mon, January 24, 2011 3:38:18 PM Subject: Re: [Utah-astronomy] Mirror Mark, Have you considered emailing Steve Dodds over at Nova Optical here in Herriman? I know when my daughter and I get done figuring our 8" and 12" mirrors I'll have him coat them. I believe he can test the mirror for you. How old is the mirror and how do the coatings look? Jay On Mon, Jan 24, 2011 at 2:29 PM, Chuck Hards <chuck.hards@gmail.com> wrote:
Mark, a quick look through a Ronchi grid will tell you everything. Likewise, before you part-out the Coulter, perform a star test. That will also tell you about the correction on the parabola.
I have owned many Coulter mirrors over the years, and never had a bad one.
On 1/24/11, Mark Shelton <woodturninginc@yahoo.com> wrote:
Hi, all
I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob.
Is there a good way to tell if the mirror is worth the effort to make a dob built around it?
I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.)
The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so.
If some one has a mirror cell to fit this size of mirror I would love to hear from you.
I really do not know what I should be looking for to check the mirror.
Any Suggestions would be appreciated.
Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
-- Jay Eads _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
You really need to do a star test and look at a planet like Saturn or Jupiter under good seeing conditions. The main problem is proper collimation and you need a center dot or reinforcement label perfectly centered on the primary to collimate it properly with a Cheshire eyepiece. See : http://www.amateurastronomy.com/tools.html. An f4.5 telescope is very sensitive to collimation. When my 10.1 " f4.5 is out of collimation everything looks mushy. When it is in collimation with good seeing I have observed Mars and Saturn at 500x with good detail and clarity. That said, I have owned two Coulter mirrors - one outstanding optically (my 10" f4.5) and the other awful (a 6" f/8 mirror in a kit). -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Mark Shelton Sent: Monday, January 24, 2011 2:10 PM To: Utah Astronomy Subject: [Utah-astronomy] Mirror Hi, all I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob. Is there a good way to tell if the mirror is worth the effort to make a dob built around it? I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.) The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so. If some one has a mirror cell to fit this size of mirror I would love to hear from you. I really do not know what I should be looking for to check the mirror. Any Suggestions would be appreciated. Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
Mark, If you have any questions, I have a friend who lives about 10 minutes from me who has made about 6 + telescopes, one being a 16 inch dob using that book as a guide and a mentor out of California. I know he would be willing to answer any questions you may have. Let me know if you want his info as you get going. Jay On Tue, Jan 25, 2011 at 9:28 AM, Don J. Colton <djcolton@piol.com> wrote:
You really need to do a star test and look at a planet like Saturn or Jupiter under good seeing conditions. The main problem is proper collimation and you need a center dot or reinforcement label perfectly centered on the primary to collimate it properly with a Cheshire eyepiece. See : http://www.amateurastronomy.com/tools.html. An f4.5 telescope is very sensitive to collimation. When my 10.1 " f4.5 is out of collimation everything looks mushy. When it is in collimation with good seeing I have observed Mars and Saturn at 500x with good detail and clarity.
That said, I have owned two Coulter mirrors - one outstanding optically (my 10" f4.5) and the other awful (a 6" f/8 mirror in a kit).
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Mark Shelton Sent: Monday, January 24, 2011 2:10 PM To: Utah Astronomy Subject: [Utah-astronomy] Mirror
Hi, all
I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob.
Is there a good way to tell if the mirror is worth the effort to make a dob built around it?
I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.)
The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so.
If some one has a mirror cell to fit this size of mirror I would love to hear from you.
I really do not know what I should be looking for to check the mirror.
Any Suggestions would be appreciated.
Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
-- Jay Eads
Thanks to Jay and Don and Eric. I am having information overload looking at some of the information available on the net. I think this will be a learning and fun project to take on. Thanks again for all the information and tips. Mark ________________________________ From: Jay Eads <jayleads@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tue, January 25, 2011 10:22:01 AM Subject: Re: [Utah-astronomy] Mirror Mark, If you have any questions, I have a friend who lives about 10 minutes from me who has made about 6 + telescopes, one being a 16 inch dob using that book as a guide and a mentor out of California. I know he would be willing to answer any questions you may have. Let me know if you want his info as you get going. Jay On Tue, Jan 25, 2011 at 9:28 AM, Don J. Colton <djcolton@piol.com> wrote:
You really need to do a star test and look at a planet like Saturn or Jupiter under good seeing conditions. The main problem is proper collimation and you need a center dot or reinforcement label perfectly centered on the primary to collimate it properly with a Cheshire eyepiece. See : http://www.amateurastronomy.com/tools.html. An f4.5 telescope is very sensitive to collimation. When my 10.1 " f4.5 is out of collimation everything looks mushy. When it is in collimation with good seeing I have observed Mars and Saturn at 500x with good detail and clarity.
That said, I have owned two Coulter mirrors - one outstanding optically (my 10" f4.5) and the other awful (a 6" f/8 mirror in a kit).
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Mark Shelton Sent: Monday, January 24, 2011 2:10 PM To: Utah Astronomy Subject: [Utah-astronomy] Mirror
Hi, all
I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob.
Is there a good way to tell if the mirror is worth the effort to make a dob built around it?
I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.)
The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so.
If some one has a mirror cell to fit this size of mirror I would love to hear from you.
I really do not know what I should be looking for to check the mirror.
Any Suggestions would be appreciated.
Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
-- Jay Eads _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
A small section of Ronchi ruling, a D-battery, switch, and grain-of-wheat bulb is all you need to make a "pocket mirror tester". Test at radius, not focus. On 1/25/11, Mark Shelton <woodturninginc@yahoo.com> wrote:
Thanks to Jay and Don and Eric. I am having information overload looking at some of the information available on the net. I think this will be a learning and fun project to take on. Thanks again for all the information and tips.
Mark
________________________________ From: Jay Eads <jayleads@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tue, January 25, 2011 10:22:01 AM Subject: Re: [Utah-astronomy] Mirror
Mark,
If you have any questions, I have a friend who lives about 10 minutes from me who has made about 6 + telescopes, one being a 16 inch dob using that book as a guide and a mentor out of California. I know he would be willing to answer any questions you may have. Let me know if you want his info as you get going.
Jay
On Tue, Jan 25, 2011 at 9:28 AM, Don J. Colton <djcolton@piol.com> wrote:
You really need to do a star test and look at a planet like Saturn or Jupiter under good seeing conditions. The main problem is proper collimation and you need a center dot or reinforcement label perfectly centered on the primary to collimate it properly with a Cheshire eyepiece. See : http://www.amateurastronomy.com/tools.html. An f4.5 telescope is very sensitive to collimation. When my 10.1 " f4.5 is out of collimation everything looks mushy. When it is in collimation with good seeing I have observed Mars and Saturn at 500x with good detail and clarity.
That said, I have owned two Coulter mirrors - one outstanding optically (my 10" f4.5) and the other awful (a 6" f/8 mirror in a kit).
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Mark Shelton Sent: Monday, January 24, 2011 2:10 PM To: Utah Astronomy Subject: [Utah-astronomy] Mirror
Hi, all
I have a question. I just acquired a 13.1 F4.5 Coulter dob. I am thinking about just using the mirror out of it and making my own version of a Obsession looking dob.
Is there a good way to tell if the mirror is worth the effort to make a dob built around it?
I have it out of the telescope and I can not see any defects so far in the mirror. ( have not looked really close at it yet.)
The Mirror sets in a kind of sling in the tube. Very Strange setup. I guess it was the way they made them in early 1980 or so.
If some one has a mirror cell to fit this size of mirror I would love to hear from you.
I really do not know what I should be looking for to check the mirror.
Any Suggestions would be appreciated.
Mark _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
-- Jay Eads _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com
participants (4)
-
Chuck Hards -
Don J. Colton -
Jay Eads -
Mark Shelton